KR20180042856A - Method and apparatus for toluene methylation in aromatics complex - Google Patents

Abstract

The disclosure of the present invention is directed to a method and apparatus for toluene methylation in an aromatics complex for the production of para-xylene. More specifically, the disclosure of the present invention is directed to a method and apparatus wherein the toluene methylation zone is incorporated into an aromatics complex for the production of para-xylene to prevent the production of benzene by-products. This can be accomplished by incorporating the toluene methylation process into the aromatics complex and recycling benzene to the aromatics complex transalkylation unit.

Description

Method and apparatus for toluene methylation in aromatics complex

Priority claims for existing US applications

This application claims priority from U.S. Patent Application No. 62 / 216,425, filed September 10, 2015, and U.S. Patent Application No. 14 / 885,265, filed October 16, 2015.

Field of the Invention

The disclosure of the present invention is directed to a method and apparatus for toluene methylation in an aromatics complex for the production of para-xylene. More particularly, the disclosure of the present invention is directed to a method and apparatus for toluene methylation in an aromatics complex for the production of para-xylene, wherein no benzene by-products are produced.

Xylene isomers are produced in large quantities from petroleum as feedstock for many important industrial chemicals. The most important of the xylene isomers is para-xylene, the main feedstock for polyester, which continues to enjoy high growth rates from a large base demand. Ortho-xylene is used to make phthalic anhydrides, which provide a large but relatively mature market. Meta-xylene is used for products such as plasticizers, azo dyes and wood preservatives in a smaller but growing amount. Ethylbenzene is generally present in the xylene mixture and sometimes recovered for styrene production, but is generally considered to be a less preferred component of the C ₈ aromatics.

Among aromatic hydrocarbons, the overall importance of xylene compete with the importance of benzene as a feedstock for industrial chemicals. Xylene and benzene are produced from petroleum by reforming naphtha, but are inadequate to meet demand and therefore require conversion of other hydrocarbons to increase the yield of xylene and benzene. Often, toluene is dealkylated to produce benzene or selectively disproportionated to produce benzene and C ₈ aromatics, from which the individual xylene isomers are recovered.

The aromatics complex flow scheme is described by Meyers in Handbook of Petroleum Refining Processes, 2d. Edition, 1997, McGraw-Hill, which is incorporated herein by reference.

Conventional aromatics complexes transfer the toluene to the transalkylation zone and transalkylate with the A ₉₊ component of the toluene to produce the desired xylene isomer. The A ₉₊ component is present on both the reformate bottom and the transalkylation effluent.

Para-xylene is most often prepared from feedstocks having a methyl to phenyl feed of less than 2. As a result, para-xylene production is limited by the available methyl groups in the feed. In addition, para-xylene preparation also typically produces benzene as a by-product. Since para-xylene is more valuable than other by-products made in benzene and aromatics complexes, there is a need to maximize the production of para-xylene from the amount of feed given. There are also cases where manufacturers of para-xylene may prefer to avoid the production of benzene or paraxylene production as a by-product. However, there are also cases where the para-xylene manufacturer may prefer to limit the production of benzene or paraxylene production as a by-product by making adjustments.

The subject of the present invention is a method and apparatus for toluene methylation in an aromatics complex for the production of para-xylene. More particularly, the disclosure of the present invention is directed to a method and apparatus for toluene methylation in an aromatics complex for the production of para-xylene, wherein no benzene by-products are produced. Integrating the toluene methylation process into the aromatics complex has several advantages. First, the integrated process can increase the amount of para-xylene that can be produced from a given amount of lipoate. The integrated process can also reduce the amount of lipomate required to produce a fixed amount of para-xylene. Second, the integrated process can avoid the production of benzene as a by-product from the aromatics complex. Both of these advantages can be achieved by incorporating the toluene methylation process into the aromatics complex and recycling benzene to the aromatics complex transalkylation unit.

Additional objects, advantages and novel features of the embodiments will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following description and the appended drawings, or may be learned by practice or practice of the embodiments. The objects and advantages of this concept may be realized and attained by means of the instrumentalities, instrumentalities and combinations particularly pointed out in the appended claims.

Figure 1 schematically shows an aromatics complex.
Figure 2 shows an aromatics complex having an integrated toluene methylation zone.
Corresponding reference symbols identify corresponding components throughout the various views of the drawings. Skilled artisans will appreciate that the components of the drawings are illustrated for simplicity and clarity and need not necessarily be drawn to scale. For example, the dimensions of some of the components in the figures may be exaggerated relative to other components to help improve understanding of various embodiments of the disclosure. Also, common but known components, which are useful or necessary in commercially viable embodiments, are not often shown to enable less of a vision of the various embodiments of the present disclosure.

Justice

As used herein, the terms "stream", "feed", "product", "portion" or "portion" refer to various hydrocarbon molecules such as linear, branched, or cyclic alkanes, alkenes, Ene, and alkyne, and optionally other materials such as gases, such as hydrogen, or impurities such as heavy metals, and sulfur and nitrogen compounds. Each of the above may also include aromatic and non-aromatic hydrocarbons.

Further, the hydrocarbon molecule may be abbreviated as C ₁ , C ₂ , C ₃ , Cn wherein "n" represents the number of carbon atoms in one or more hydrocarbon molecules, or the reduction may be, for example, Can be used as an adjective for. Similarly, an aromatic compound can be abbreviated as A ₆ , A ₇ , A ₈ , An, where "n" represents the number of carbon atoms in one or more aromatic molecules. Further, the superscript "+" or "-" may be used in conjunction with one or more abbreviated hydrocarbon notations such as C _{3 +} or C _{3 -} , which contain one or more hydrocarbons condensed. By way of example, the abbreviation "C _{3 +} " means one or more hydrocarbon molecules of three or more carbon atoms.

As used herein, the term "zone" may refer to an area that includes one or more equipment items and / or one or more sub-zones. Equipment items may include, but are not limited to, one or more reactors or reaction vessels, separation vessels, distillation columns, heaters, exchangers, pipes, pumps, compressors, and conditioners. Additionally, the item of equipment, such as a reactor, dryer, or vessel, may further include one or more zones or sub-zones.

As used herein, the term "rich" may mean an amount of at least generally 50 mol%, preferably 70 mol%, of the compound or class of compounds in the stream.

Carrying out the invention  Specific details for

The following description is not to be taken in a limiting sense, but merely for the purpose of describing the general principles of the exemplary embodiments. The scope of the present disclosure should be determined with reference to the claims.

The feed stream to the process of the present invention is generally represented by the general formula C₆H_(6-n)R_nWherein n is an integer from 0 to 5 and each R is an arbitrary combination of CH₃, C₂H₅, C₃H₇, Or C₄H₉Lt; / RTI > The aromatics-rich feed stream to the process of this disclosure can be derived from a variety of feedstocks, including but not limited to contact reforming, light olefins, and heavier aromatics-rich byproducts (often referred to as "pygas" Steam pyrolysis of naphtha, distillates or other hydrocarbons to obtain gasoline-range materials referred to as " gasoline-range "), and catalytic or thermal cracking of distillates and heavy oils to obtain products in the gasoline range . Pyrolysis or other cracking operations are generally known in the industry prior to being charged to the complex to remove sulfur, olefins and other compounds that may affect the product quality and / or damage the catalyst or adsorbent used therein. Lt; / RTI > The light cycle oil from catalyst cracking can also advantageously be hydrotreated and / or hydrogen cracked according to known techniques to obtain products in the gasoline range; The hydrotreating preferably also comprises catalytic reforming to obtain an aromatic compound rich feed stream. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a simplified flow diagram of an exemplary aromatics-processing complex of known art for the preparation of one or more xylene isomers. The complex can, for example, process an aromatic compound-rich feed derived from catalytic reforming in the reforming zone 6. The reforming zone generally comprises a reforming unit (4) for receiving feed through a conduit (2). The reforming unit typically comprises a reforming catalyst. Usually this stream will also be treated to remove olefin compounds and light ends, such as butane and lighter hydrocarbons and preferably pentane; However, such removal is not necessary and is not indicative of the practice of the broad aspect of the disclosure. The aromatics containing feed stream comprises benzene, toluene and C₈  Containing aromatic compounds and usually containing heavier aromatic compounds and aliphatic hydrocarbons, including naphthenes.

The feed stream is passed through the conduit 10 through the heat exchanger 12 to the reformate splitter 14 and from the toluene and harder hydrocarbon recovered overhead via the conduit 18 to the through the bottom discharge port 15 it is pulled out as a bottom stream, and C ₈ is distilled to separate the more streams including aromatic compounds of the heavy. Toluene and lighter hydrocarbons are transferred to the extractive distillation unit 20 which separates predominantly aliphatic raffinate from the conduit 21 from the benzene-toluene aromatics stream in the conduit 22. The aromatics stream in conduit 22 is fed to the benzene column 23 via the stripped transalkylation product in conduit 45 and overhead from the para-xylene finishing column in conduit 57, Stream and the toluene- and-heavy aromatic compound stream in conduit 25, which is transferred to the toluene column 26. Toluene is the recovered overhead from the column in conduit 27 and can be transferred to the transalkylation unit 40, in part or in full, as shown and discussed below.

The bottom stream from the toluene column 26 passes through the conduit 28 with the bottom of the reformate splitter in the conduit 16 (after treatment through the clay processor 17) ) it is recycled in the C ₈ aromatics to the fractionator 30. The fractionator 30 separates the concentrated C ₈ aromatics as overhead in the conduit 31 from the high boiling stream comprising C ₉ , C ₁₀ and heavier aromatics as the bottom stream in conduit 32 . This bottoms stream is passed to the heavy column (70) via conduit (32). The heavy aromatic compound column contains C ₉ and at least some C ₁₀ and C ₁₁ aromatics, together with a higher boiling compound, which is a predominantly heavier alkyl aromatic compound drawn as a bottoms stream through conduit 72 Providing an overhead stream in conduit 71.

The heavy column C ₉ + aromatics in conduit 71 are combined with the toluene containing overhead contained in conduit 27 as feed to transalkylation reactor 40; This includes the transalkylation catalyst, such as those known in the art to produce a transalkylation product containing benzene to C ₁₁ + aromatics to the center of the xylene therefrom. The transalkylation product in conduit 41 is stripped at stripper 42 to return to extractive distillation 20 via conduit 44 for recovery of gas and light aromatics in conduit 43 and purification of benzene C ₆ and harder hydrocarbons are taken out. The bottom of the stripper origin is transferred to the benzene column 23 via conduit 45 to recover the benzene product and unconverted toluene.

C ₈ provided by the fractionator 30-aromatics overhead is para-xylene, meta-xylene, ortho-including xylene and ethylbenzene and para-through conduit (31) passing through the xylene separation step (50) do. The separation process preferably operates through adsorption using an absorbent to provide a mixture of para-xylene and an absorbent through the conduit 51 to the extraction column 52, which causes para-xylene through the conduit 53 Separating from the return absorbent in conduit 54; Para-xylene is refined in finishing column 55 to obtain a hard material through para-xylene product and conduit 57 and back to benzene column 23 via conduit 56. The non-equilibrium mixture of the C ₈ -aromatic compound raffinate and the sorbent from the separation process 50 is conveyed through the conduit 58 to the raffinate column 59 from the return absorbent in conduit 61 to the conduit 60, Lt; RTI ID = 0.0 > isomerization < / RTI >

The raffinate, which contains a non-equilibrium mixture of xylene isomer and ethylbenzene, is conveyed via conduit 60 to the isomerization reactor 62. The raffinate is isomerized in reactor 62, which comprises an isomerization catalyst to provide a product that reaches the equilibrium concentration of the C ₈ -aromatic isomer. The product is passed via conduit 63 to deheptanator 64 which removes C ₇ and lighter hydrocarbons with a bottom that is passed through conduit 65 to xylene column 30 to provide isomerization And separates the C ₉ and heavier materials from the resulting C ₈ -aromatic compound. The overhead liquid derived from the deheptane 64 is transferred to the stripper 66 which removes the hard material overhead in the conduit 67 from the C ₆ and C ₇ material which is used to recover the benzene and toluene values, (68) to the extractive distillation unit (20).

As will be appreciated by the skilled artisan, there are many possible variations of the scheme within the skill of the art. For example, only the entire C ₆ -C ₈ lipoate or benzene containing moiety can be treated with extraction. Para-xylene can be recovered from the C ₈ -aromatic mixture by crystallization rather than adsorption. Meta-xylene and also para-xylene can be recovered from the C ₈ -aromatic mixture by adsorption, and ortho-xylene can be recovered by fractionation. Alternatively, the C < ₉ > - and heavier stream or heavy aromatic stream may be processed by solvent extraction using a polar solvent or solvent distillation or stripping with steam or other media to form a highly condensed aromatic compound C ₉ + recycle to transalkylation. In some cases, the entire heavier aromatic stream can be processed directly in the transalkylation unit. The disclosure of the present invention is useful in these and other variations of the aromatics-processing scheme, aspects of which are described in US 6,740,788, which is incorporated herein by reference.

Referring now to FIG. 2, an aromatics complex and process according to one embodiment will be illustrated and described, wherein the aromatics complex comprises an integrated toluene methylation zone. Figure 2 is a simplified flow diagram of an exemplary aromatics-processing complex of the known art integrated with a toluene methylation unit for the production of one or more xylene isomers. The complex can, for example, process an aromatic compound-rich feed derived from catalytic reforming in the reforming zone 6. The reforming zone generally comprises a reforming unit (4) for receiving feed through a conduit (2). The reforming unit will typically comprise a reforming catalyst. Usually this stream will also be treated to remove olefin compounds and low boiling materials such as butane and lighter hydrocarbons and preferably pentane; However, such removal is not necessary and is not indicative of the practice of the broad aspect of the disclosure. The aromatics containing feed stream comprises benzene, toluene and C₈  Containing aromatic compounds and usually containing heavier aromatic compounds and aliphatic hydrocarbons, including naphthenes.

The feed stream is passed through the conduit 10 through the heat exchanger 12 to the reformate splitter 14 and from the toluene and harder hydrocarbon recovered overhead via the conduit 18 to the through the bottom discharge port 15 it is pulled out as a bottom stream, and C ₈ is distilled to separate the more streams including aromatic compounds of the heavy. Toluene and lighter hydrocarbons are transferred to the extractive distillation unit 20 which separates predominantly aliphatic raffinate from the conduit 21 from the benzene-toluene aromatics stream in the conduit 22. The aromatics stream in conduit 22 is combined with the stripped transalkylation product in conduit 45, the overhead from para-xylene finishing column in conduit 57, and the light aromatic stream in conduit 88, Is separated into a benzene stream in conduit 24 and a toluene- and heavy aromatic stream in conduit 25 in column 23 which is transferred to toluene column 26. The benzene stream in conduit 24 is passed from benzene column 23 to transalkylation unit 40. In one embodiment, the transalkylation conditions may include a temperature of 320 ° C to 440 ° C. The transalkylation zone may comprise a first catalyst. In one embodiment, the first catalyst comprises at least one zeolite component suitable for transalkylation, at least one zeolite component suitable for dealkylation, and at least one metal component suitable for hydrogenation. Toluene is the recovered overhead from the column in conduit 27 and can be transferred to the toluene methylation unit 80, partially or fully, together with the methanol stream in conduit 82, as shown and discussed below.

The methanol stream in the conduit 82 and the toluene in the conduit 27 are passed to the toluene methylation unit 80 and produce a hydrocarbon stream in the conduit 84. The hydrocarbon stream in conduit 84 is passed to column 90 which produces an overhead stream in conduit 86 and a bottom stream in conduit 88. The bottom stream in conduit 88 is transported back to the benzene column 23. In one embodiment, the toluene methylated product stream has a ratio of para-xylene to total xylene of 0.2 or greater, preferably 0.5 or greater, more preferably 0.8 to 0.95.

The downstream process is shown in Fig. C ₈ provided by the fractionator 30-aromatics overhead is para-xylene, meta-xylene, ortho-including xylene and ethylbenzene and para-through conduit (31) passing through the xylene separation step (50) do. The separation process preferably operates through adsorption using an absorbent to provide a mixture of para-xylene and an absorbent through the conduit 51 to the extraction column 52, which causes para-xylene through the conduit 53 Separating from the return absorbent in conduit 54; Para-xylene is refined in finishing column 55 to obtain a hard material through para-xylene product and conduit 57 and back to benzene column 23 via conduit 56. The non-equilibrium mixture of the C ₈ -aromatic compound raffinate and the sorbent from the separation process 50 is conveyed through the conduit 58 to the raffinate column 59 from the return absorbent in conduit 61 to the conduit 60, Lt; RTI ID = 0.0 > isomerization < / RTI >

The raffinate, which contains a non-equilibrium mixture of xylene isomer and ethylbenzene, is conveyed via conduit 60 to the isomerization reactor 62. The raffinate is isomerized in reactor 62, which comprises an isomerization catalyst to provide a product that reaches the equilibrium concentration of the C ₈ -aromatic isomer. In one embodiment, the isomerization conditions comprise a temperature of 240 < 0 > C to 440 < 0 > C. In addition, the isomerization zone comprises a second catalyst. In one embodiment, the second catalyst comprises at least one zeolite component suitable for xylene isomerization, at least one zeolite component suitable for ethylbenzene conversion, and at least one metal component suitable for hydrogenation. In one embodiment, the isomerization process is carried out in the vapor phase. In another embodiment, the isomerization process is carried out in a liquid phase. In one embodiment, the isomerization process converts benzene to benzene by dealkylation. In another embodiment, the isomerization process converts xylenes to xylenes by isomerization.

The product is passed via conduit 63 to deheptane 64 which removes the C ₇ and higher hard hydrocarbons with the bottom passing through xylene column 30 through conduit 65 to provide isomerization And separates the C ₉ and heavier materials from the resulting C ₈ -aromatic compound. The overhead liquid derived from the deheptane 64 is transferred to the stripper 66 which removes the hard material overhead in the conduit 67 from the C ₆ and C ₇ material which is used to recover the benzene and toluene values, (68) to the extractive distillation unit (20).

As will be appreciated by the skilled artisan, there are many possible variations of the scheme within the skill of the art. For example, only the entire C ₆ -C ₈ lipoate or benzene containing moiety can be treated with extraction. Para-xylene can be recovered from the C ₈ -aromatic mixture by crystallization rather than adsorption. The separation zone may also include a simulated moving bed adsorption unit. In one example, the simulated moving bed adsorption unit utilizes a sorbent having a lower boiling point than xylene, such as toluene or benzene. In yet another embodiment, the simulated moving bed adsorption unit utilizes a sorbent having a boiling point higher than xylene, such as paradiethylbenzene, paradiisopropylbenzene, tetralin, or paraethyltoluene. Meta-xylene and also para-xylene can be recovered from the C ₈ -aromatic mixture by adsorption, and ortho-xylene can be recovered by fractionation. Alternatively, the C < ₉ > - and heavier stream or heavy aromatic stream may be processed by solvent extraction using a polar solvent or solvent distillation or stripping with steam or other media to form a highly condensed aromatic compound C ₉ + recycle to transalkylation. In some cases, the entire heavier aromatic stream can be processed directly in the transalkylation unit. The disclosure of the present invention is useful in these and other variations of the aromatics-processing scheme, aspects of which are described in US 6,740,788, which is incorporated herein by reference.

[Example]

The following examples are intended to further illustrate embodiments of the invention. The examples of these different embodiments are not intended to limit the claims of the specific details of the embodiments.

case: Comparative Example Example 1 Example 2 Including toluene methylation? Not included Included Included Xylene isomerization type EB dealkylation EB dealkylation EB isomerization Feed flow rate, MT / yr X 1,000 Lipomate 1703 1140 1159 Methanol 0 340 304 Hydrogen 8 9 9 Product flow rate, MT / yr X 1,000 p-xylene 1000 1000 1000 benzene 376 0 0 Heavy aromatic compounds 45 42 49 Sulpolan raffinate 173 116 123 water 0 191 171 Low-boiling substance 117 141 129

The table above demonstrates the benefit of having an integrated toluene methylation zone integrated within the aromatics complex. As shown in the Table, Example 1 illustrates an aromatics-processing complex for the production of para-xylene without benzene by-products according to the invention as illustrated in Fig. In the above example, the xylene isomerization unit converts ethylbenzene by dealkylation. In addition, as shown in the table, Example 2 illustrates an aromatics-processing complex for the production of para-xylene without benzene by-products according to the invention as illustrated in Fig. In the above example, the xylene isomerization unit converts ethylbenzene by isomerization.

It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such variations and modifications may be made without departing from the spirit and scope of the subject matter of the present invention and without diminishing its attendant advantages.

Specific embodiments

It is to be understood that the description is intended to be illustrative and not restrictive of the scope of the appended claims and the appended claims.

A first embodiment of the present invention is a process for preparing para-xylene without benzene by-products, said process comprising the steps of passing a benzene-containing hard aromatic stream and a C ₉ -C ₁₀ aromatics-containing heavy aromatic stream through a transalkylation zone ; Treating the light aromatic stream and the heavy aromatic stream in the transalkylation zone with transalkylation conditions comprising the presence of a first catalyst to provide a greater concentration of toluene to the C ₈ aromatics to provide a transalkylation product stream; From the transalkylation product stream, a first boiling fraction comprising benzene, a second boiling fraction comprising toluene, a third boiling fraction comprising C ₈ aromatics and a fourth boiling fraction comprising C _{9 +} aromatics are fractionated ; ≪ / RTI > Recycling at least a portion of the benzene from the transalkylation product stream back to the transalkylation zone; Passing at least a portion of the second boiling fraction from step c, g and i and a methanol stream to a toluene methylation zone operating under toluene methylation conditions to produce a toluene methylated product stream; Separating the same fraction as described in step c from the toluene methylated product stream by fractionation; Selectively removing the xylene product and provides a non-equilibrium mixture of C ₈ aromatics - step c, g, and by processing at least a portion of the third boiling fraction containing the C ₈ aromatic compound i in discrete areas para; Treating a non-equilibrium mixture of C ₈ aromatics with xylene isomerization conditions comprising the presence of a second catalyst to provide an isomerization product; And separating the same fraction described in step c by fractionation from the isomerization product stream. One embodiment of the present invention is one, some or all of the previous embodiments of this paragraph up to the first embodiment of this paragraph, wherein the transalkylation conditions comprise a temperature of 320 [deg.] C to 440 [deg.] C.

One embodiment of the present invention is the first implementation of this paragraph, wherein the first catalyst comprises at least one zeolite component suitable for transalkylation, at least one zeolite component suitable for dealkylation, and at least one metal component suitable for hydrogenation. Some, or all of the previous embodiments of the present paragraph to the embodiments. One embodiment of the present invention is a process for preparing a toluene methylated product stream wherein the toluene methylated product stream has a ratio of para-xylene to total xylene of at least 0.2, preferably at least 0.5, more preferably from 0.8 to 0.95. Some, or all of the previous embodiments of the paragraph. One embodiment of the present invention is one, some or all of the previous embodiments of this paragraph up to the first embodiment of this paragraph, wherein the isomerization conditions comprise a temperature of from 240 캜 to 440 캜. One embodiment of the present invention is directed to a process for the preparation of a zeolite of the present invention wherein the second catalyst comprises at least one zeolite component suitable for xylene isomerization, at least one zeolite component suitable for ethylbenzene conversion, and at least one metal component suitable for hydrogenation. Some, or all of the previous embodiments of this paragraph up to the first embodiment. One embodiment of the present invention is one, some or all of the previous embodiments of this paragraph up to the first embodiment of this paragraph, wherein the isomerization process is carried out in the vapor phase. One embodiment of the present invention is a process for the preparation of benzene by converting one or more, or all, of the previous embodiments of this paragraph to the first embodiment of this paragraph, wherein the isomerization process converts benzene to ethyl benzene by dealkylation. to be. One embodiment of the present invention is a process for the preparation of one, some or all of the previous embodiments of this paragraph up to the first embodiment of this paragraph, wherein the isomerization process converts xylenes to ethylbenzene by isomerization. to be. One embodiment of the present invention is one, some or all of the previous embodiments of this paragraph up to the first embodiment of this paragraph, wherein the isomerization process is carried out in liquid phase.

One embodiment of the present invention is one, some or all of the previous embodiments of this paragraph up to the first embodiment of this paragraph, wherein all of the benzene is recycled to the transalkylation zone. One embodiment of the present invention is one, some or all of the previous embodiments of this paragraph up to the first embodiment of this paragraph, wherein the separation zone comprises a crystallization unit. One embodiment of the present invention is one, some or all of the previous embodiments of this paragraph up to the first embodiment of this paragraph, wherein the separation zone comprises a simulated moving bed adsorption unit. One embodiment of the present invention is one, some or all of the previous embodiments of this paragraph up to the first embodiment of this paragraph, wherein the simulated moving bed adsorption unit utilizes a sorbent having a lower boiling point than xylene, such as toluene or benzene . One embodiment of the present invention is directed to a process for preparing the same, wherein the simulated moving bed adsorbent unit is an adsorbent of the first embodiment of this paragraph using an absorbent having a boiling point higher than that of xylene such as paradiethylbenzene, paradiisopropylbenzene, tetralin or paraethyltoluene. Some, or all of the previous embodiments of this paragraph.

One embodiment of the present invention is a process for the preparation of a C ₈ aromatic fraction from a toluene methylation unit derived from a further C ₈ aromatic fraction produced in the process, Some, or all of the previous embodiments of this paragraph. One embodiment of the present invention is a process for the preparation of the first embodiment of this paragraph wherein the C ₈ aromatic fraction prepared in the toluene methylation unit is processed in the same separation zone as one or more other C ₈ aromatic fractions but is introduced at a different feed location Some or all of the previous embodiments of this paragraph up to < / RTI > One embodiment of the present invention is directed to a process for preparing a C ₈ aromatic fraction, wherein the C ₈ aromatic fraction prepared in the toluene methylation unit is processed in a separation zone separated from the separation zone used for the other C ₈ aromatic fraction Some, or all of the previous embodiments of this paragraph. One embodiment of the present invention is a process for the preparation of a C ₈ aromatic fraction prepared in a toluene methylation unit, wherein one of the previous embodiments of this paragraph up to the first embodiment of this paragraph, wherein the C ₈ aromatic fraction produced in the toluene methylation unit is processed in a separation zone comprising a crystallization unit , Some or all. One embodiment of the present invention is directed to a method of making a C ₈ aromatics fraction produced in a toluene methylation unit that is processed in a separation zone comprising a simulated moving bed adsorption unit, One, some or all of the modes.

A second embodiment of the present invention is an apparatus for the production of para-xylene comprising a transalkylation zone in fluid communication with a toluene methylation zone wherein the toluene methylation zone is in fluid communication with the aromatics separation zone and the aromatics separation zone is an isomerization zone Lt; / RTI >

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent and readily ascertain the essential characteristics of the invention so as to provide a broad and broad disclosure of the various embodiments of the present invention without departing from the spirit and scope of the invention. Modifications and variations thereof, which can be adjusted in various ways and with various uses. Accordingly, the foregoing preferred specific embodiments are to be considered as illustrative only and not to be limiting in any way to the remainder of the disclosure in any way whatsoever, and it is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims. . In this context, unless otherwise stated, all temperatures are listed in degrees Celsius, and all parts and percentages are by weight.

Claims (10)

A process for the preparation of para-xylene without benzene by-products,
Passing a benzene-containing light aromatic stream and a C ₉ -C ₁₀ aromatic-containing heavy aromatic stream to a transalkylation zone;
Treating the light aromatic stream and the heavy aromatic stream in the transalkylation zone with transalkylation conditions comprising the presence of a first catalyst to provide a greater concentration of toluene to the C ₈ aromatics to provide a transalkylation product stream;
From the transalkylation product stream, a first boiling fraction comprising benzene, a second boiling fraction comprising toluene, a third boiling fraction comprising C ₈ aromatics and a fourth boiling fraction comprising C _{9 +} aromatics are fractionated ; ≪ / RTI >
Recycling at least a portion of the benzene from the transalkylation product stream back to the transalkylation zone;
Passing at least a portion of the second boiling fraction from step c, g and i and a methanol stream to a toluene methylation zone operating under toluene methylation conditions to produce a toluene methylated product stream;
Separating the same fraction as described in step c from the toluene methylated product stream by fractionation;
Selectively removing the xylene product and provides a non-equilibrium mixture of C ₈ aromatics - step c, g, and by processing at least a portion of the third boiling fraction containing the C ₈ aromatic compound i in discrete areas para;
Treating a non-equilibrium mixture of C ₈ aromatics with xylene isomerization conditions comprising the presence of a second catalyst to provide an isomerization product; And
Separation of the same fraction described in step c by fractionation from the isomerization product stream
≪ / RTI > wherein the para-xylene is free of benzene by-products. 2. The process of claim 1, wherein the first catalyst comprises at least one zeolite component suitable for transalkylation, at least one zeolite component suitable for dealkylation, and at least one metal component suitable for hydrogenation. 2. A process according to claim 1, wherein the toluene methylated product stream is such that the ratio of para-xylene to total xylene is at least 0.2, preferably at least 0.5, more preferably from 0.8 to 0.95. The process of claim 1, wherein the second catalyst comprises at least one zeolite component suitable for xylene isomerization, at least one zeolite component suitable for ethylbenzene conversion, and at least one metal component suitable for hydrogenation. The process according to claim 1, wherein the isomerization step is carried out in a vapor phase. The process according to claim 1, wherein the isomerization step is carried out in a liquid phase. The process according to claim 1, wherein all of the benzene is recycled to the transalkylation zone. The method according to claim 1, wherein the separation zone comprises a crystallization unit. The method of claim 1, wherein the separation zone comprises a simulated moving bed adsorption unit. And a transalkylation zone in fluid communication with the toluene methylation zone, wherein the toluene methylation zone is in fluid communication with the aromatics separation zone, and wherein the aromatics separation zone is in fluid communication with the isomerization zone, Apparatus for producing para-xylene.

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